1. Field of the Invention
The present invention relates to a method for producing at least one fluid contained in a geological formation by means of substantially horizontal drains, when this formation contains at least a second fluid which risks hindering production of the first.
In this description, the term "drain" is essentially used for designating an artificial well serving for draining a formation, this well possibly comprising over a portion of its length at least one perforated tube.
However, the present invention may be applied to a natural drain, if it has an appropriate form and layout.
2. Description of the Prior Art
When it is desired to produce one of two fluids present, for example oil, there occurs under the effect of the pressure gradient due to the desired flow of the fluid to be recovered, a deformation of the surface separating the two fluids which will be termed ridge effect. This is described in the article by Mr. GIGER entitled "EVALUATION THEORIQUE DE L'EFFET D'ARETE D'EAU SUR LA PRODUCTION PAR PUITS HORIZONTAUX" published in the revue of the French petroleum institute vol. 38, No 3, pages 361-370, May-June 1983, Paris (France). This ridge effect may cause a breakthrough of the undesired fluid and, consequently, the production of the undesired fluid in considerable proportions which may adversely effect working of the oil from an economic point of view.
The present invention avoids this disadvantage.
The prior art may be illustrated by the following U.S. Pat. Nos. 2,889,880; 3,638,731 and 2,855,047.
The methods described in these prior patents require the formation impregnated by the different fluids (gas, oil, water) to have passing therethrough the same oil used for producing the desired fluid, even if the production is made selective by addition of plugs and tubes.
These methods are defective and without effect if the geological formation is brought into yield by means of horizontal or very slanted drains.
More precisely, the present invention provides a method for producing a first fluid or desired fluid contained in a geological formation, this formation further comprising at least a second fluid or undesired fluid which risks hindering production of the first fluid, this first fluid being produced by means of at least one deflected or substantially horizontal first drain.